System devices including NICs for transmitting/receiving data through a network to provide various network services to external devices connected to the network include, for example, digital multi-function peripherals (hereinafter, MFPs), which are image forming apparatuses.
Recently, these MFPs perform general image processes, such as a scanner image process and image generation for printers, and processes such as input/output interface control, and have a multi-CPU configuration including a NIC CPU responsible for input/output data control for a connected network and an MFP CPU responsible for other processes.
An MFP controller is responsible for network services provided by the MFP and having various processing load level of the NIC CPU, for example, color scan network transmission, responses to web accesses, and responses to inquiries for MFP statuses.
Some network services closely relate to data encryption processes due to the nature of the services and a function may be included in some cases to use a dedicated encryption chip to execute the processes at high speed.
On the other hand, if no operation is performed or no data transmission/reception is performed for external devices connected to the network for a predetermined time period or more, the MFPs are conventionally shifted to an energy-saving mode by turning off a fixing heater, a printer controller, etc.
For example, Japanese Laid-Open Patent Publication No. 2003-089254 discloses a technology of driving an input/output portion to execute processes for network monitoring and data transmission/reception such that data can be transmitted/received even when an image forming apparatus is shifted to the energy-saving mode. Japanese Laid-Open Patent Publication No. 2004-110215 discloses a technology of putting an image forming apparatus into the power-saving state if it is detected that all the host computers connected through a network are turned off.
Japanese Laid-Open Patent Publication No. 7-321874 discloses a data communication apparatus that changes a clock frequency of a data processing CPU depending on communication speed to achieve power saving.
However, the conventional arts of Japanese Laid-Open Patent Publication No. 2003-089254 or 2004-110215 do not achieve the power-saving operation of the NIC itself, and the conventional art of Japanese Laid-Open Patent Publication No. 7-321874 only changes the operation clock frequency of the data processing CPU and cannot achieve reasonable power-saving operation corresponding to a plurality of functions included in the NIC.
For example, in the case of the NIC equipped with an encryption chip, although the high-speed processing ability of the encryption chip is effectively utilized for the “color scan network transmission”, which is a network service with a high NIC CPU processing load, excessive electric power is problematically consumed for the “responses to inquiries for MFP statuses”, which is a network service with a low processing load, since the process of the similar/same level is executed.